For ADHD, based on a case-control study completed several years ago in a local school district, we have submitted a manuscript on ADHD prevalence among elementary school children. Using our epidemiologic case definition, 15.5% of children in grades 1-5 in this school district had ADHD. Though higher than many estimates, ours is based on systematic screening of all children in the schools and so captures children who may not be evaluated in studies involving clinical diagnoses. Future work will address maternal stress during pregnancy as a possible risk factor for ADHD. (see Z01 ES49034; PI Dale Sandler, EB We have used data from the Agricultural Health study to examine specific pesticides as risk factors for ALS. Organochlorines in general and dieldrin in particular showed evidence of association with ALS although the small number of cases limited precision of estimation. We are planning to examine military and occupational exposures as risk factors for ALS in collaboration with researchers at Duke University and the Durham Veterans Administration Hospital using data from a case-control study of U.S. veterans. (see Z01 ES49005; LI Freya Kamel, EB) We have carried out a case-control study nested within the Agricultural Health Study to examine associations between Parkinson's disease and environmental risk factors, particularly certain pesticide exposures. We are also looking at selected candidate genes as susceptibility factors. This study employs data from the Agricultural Health Study as well as additional questionnaire data and field samples collected expressly for this effort. We have reported that the risk of Parkinson's disease associated with head injury increases dramatically when the subject carries certain alpha-synuclein genetic variants. Analysis of data is ongoing. (see Z01 ES44007 EB; LI Freya Kamel, EB) Data collection for a study of the effects of soy estrogen on neonatal development is underway at Childrens Hospital of Philadelphia. We are currently working with two commercial laboratories and the CDC to resolve some interlaboratory differences in testosterone measurements. We are also characterizing the performance of methods for cytological assessment of vaginal and urethral epithelium in infants. (see Z01 ES44006 EB; PI Walter Rogan, EB)